1. Field of the Invention
This invention relates in general to submersible centrifugal pumps, and in particular to wear resistant inserts located in the pump stages for reducing erosion and/or abrasion.
2. Description of the Prior Art
A submersible centrifugal pump assembly of the type concerned herein includes a downhole electric motor coupled to a centrifugal pump. The pump has numerous stages of diffusers and impellers for pumping fluid to the surface from the well. Normally the impellers and diffusers are made from a cast alloy. The impellers rotate within the diffusers, and the mating sliding surfaces are machined smooth to reduce wear and to provide close clearances for sealing. Elastomeric thrust washers may be located between the impellers and diffusers to avoid metal-to-metal contact in the direction of downward and upward thrust.
While these types of pumps are successful, if the fluid being pumped contains a significant amount of entrained sand, the abrasive particles will abrade and/or erode the pump impellers and diffusers, shortening the life of the pump. Normally a pump needs to be pulled from the well for servicing only every twelve to eighteen months. If the sand has abraded the pump components severely, the pump might have to be pulled earlier than the usual life. The cost for pulling the pump, including lost production time, can be quite expensive, particularly with offshore wells.